The present invention relates to a method of occluding an aperture in a body. More specifically, the present invention relates to an occlusion device for occluding a septal defect having five or more arms.
The heart is generally comprised of four chambers, the left and right atrium and the left and right ventricle. Separating the left and right sides of the heart are two walls, or septa. The wall between the two atria is the interatrial septum, and the wall between the two ventricles is the interventricular septum. There are several defects which can affect the septa of both children and adults, including patent ductus arteriosus, patent foramen ovate, atrial septal defects (ASDs), and ventricular septal defects (VSDs).
Normally, permanently repairing septal or other cardiac defects in adults and children requires open heart surgery, a high risk, painful, and costly procedure. In response to these concerns, modern occlusion devices have been developed are that small enough to be delivered through a catheter. Rather than surgery, these occlusion devices are deployed by inserting a catheter into a major blood vessel and moving the occlusion device through the catheter. This type of procedure can be performed in a cardiac cathlab, and avoids much of the risks, cost, and pain associated with open heart surgery. These modern occlusion devices can be used to treat a wide range of cardiac defects, including patent ductus arteriosis, patent foramen ovale, atrial septal defects, ventricular septal defects, and can be used to occlude other cardiac and non-cardiac apertures.
Occlusion devices that can be inserted via a catheter include button devices, collapsible umbrella-like structures, and plug-like devices. Occlusion devices with umbrella-like structures use a system of small metal wires to hold the occlusion device in place. When designing such occlusion devices, there are several design constraints due to the severe environment the human heart presents, including a continuous cycling of up to 5 billion pulses over the lifetime of a human.
First, the occlusion device must be stiff enough and have enough tension so that the occlusion device will remain in place even as the heart pulses. Second, the occlusion device must have a high cycle life, so that it does not develop fatigue failure problems due to the constant flexing of portions of the occlusion device caused by the beating heart. Lastly, the device must have a suitable tactile response so that when it is deployed, the physician can “feel” whether or not the device has been successfully deployed at the defect.
Each of these constraints competes with the other, making it difficult to design an occluder which adequately addresses all of them. Increasing stiffness may increase the tactile response, but may also lead to a decreased cycle life. This is because increasing the stiffness typically involves varying the shape and increasing the diameter of the wires used in occlusion devices. However, increasing the diameter of the wire to improve its stiffness or strength often reduces the cycle life because a larger diameter wire is often more brittle, and thus more susceptible to fatigue failure. Conversely, using smaller, thinner wires may result in increase fatigue life, but may also reduces the ability of the occlusion device to successfully occlude the defect, and may adversely affect the tactile response felt by the physician.
Yet another design criteria for designing an occlusion device is to ensure that the occluder seats properly. Because every patient's heart is different, and because it is extremely rare for the surfaces of the heart to be smooth and even, it is difficult to ensure that the occlusion device properly matches the contours of the defect to be occluded.
Thus, there is a need in the art for an occlusion device with a high fatigue life that has enough tension so that the occlusion device stays in place and provides the desired feel to a physician. There is also a need in the art for improved conformance to the defect to be occluded.